1. Field of the Invention
The present invention relates to an image pickup apparatus for generating and recording a plurality of image data in different recording formats in one-time image capturing and a control method thereof.
2. Description of the Related Art
For digital cameras, various recording formats are proposed for storing a still image obtained by electrically converting an analog signal obtained from image pickup devices, for example, charge-coupled device (CCD) sensors or complementary metal oxide semiconductor (CMOS) sensors, into digital data. In such digital cameras, it is common to compress the digital data obtained from the image pickup devices using a lossy algorithm, and store the compressed image data, whose data size is smaller than the original data size, into a recording medium. When image data is compressed, a processor specifically designed for image processing can adjust color tones or contrast so as to match a user's taste, and the size of an image or the compression ratio of the image can be set arbitrarily by the user. Thus, after the image is taken, there is no need to perform processing on the image data again with an application software program executed on a personal computer (PC). In addition, since the image data is compressed, more images can be stored in the recording medium. That is, more pictures can be taken. Joint Photographic Experts Group (JPEG) format is widely used as a major compression format.
On the other hand, a non-compressed format (hereinafter referred to as RAW format or RAW data) in which digital data converted from an analog electric signal supplied from image pickup devices is simply stored into a recording medium is also used. In this format, since the digital data is not compressed, after an image is taken, a user can arbitrarily set and adjust, for example, color tones, brightness, saturation, and contrast by using an application software program executed on a PC. Thus, defects in the taken image can be retouched, and moreover the taken images can be corrected or modified in a more flexible manner. Assuming that a similar image correction operation is performed on the compressed image data, compared with the case of RAW data, not only are the possible types of processing limited but also such processing may greatly degrade the compressed image data. This is because when the original image data is compressed to obtain the compressed image data, a large amount of original image data information is lost.
However, there is a problem that a file size of image data is larger in RAW format than in a compressed format. Thus, the number of image data capable of being stored in a recording medium is limited. Since an image file in RAW format is large, such an image file requires a longer time to be recorded in the recording medium. In order to solve this problem, recently, a digital camera has been developed which is capable of changing the size of image data in RAW format by performing a data processing operation before and after taking the image. For such a digital camera, the setting can be changed in response to a purpose of taking an image or the capacity of a recording medium, and thus the degree of freedom in taking the image is improved.
Japanese Patent Laid-Open No. 2004-260813 discloses a technology of reducing a resolution (the number of pixels) of RAW data. According to this, the size of RAW data can be reduced to a size specified by a user, and thus the file size required for the RAW data is reduced and the writing speed for the reduced file is increased. Both RAW data and compressed data have advantages and disadvantages, and many proposals for reducing the disadvantages have been made.
Many formats are available for recording data, and some digital cameras can simultaneously record image data in two recording formats when taking an image. Relatively many users use this mode since RAW data and compressed data can be simultaneously recorded in one-time image capturing. Moreover, since recording formats and the size of image data can be arbitrarily set, file management can be performed flexibly in response to a photographer's purpose or the capacity of a recording medium.
However, if each of RAW format, JPEG format, and the like has many image-size choices, the number of combinations of image size and format greatly increases. In particular, in the case of recording image data in a plurality of formats simultaneously, a user is required to select a desired combination, which serves as a desired setting, among many combinations. As a result, the usability of such a system decreases even though the user has more choices regarding format and image size. In addition, since specifying the setting is complicated, there are the following disadvantages for users. For example, users may miss releasing the shutter at the right moment or select an undesired setting.